The Vertical Structure of Planet-induced Gaps in Proto-Planetary Discs

TL;DR

This paper investigates the vertical structure of planet-induced gaps in protoplanetary discs, revealing how spiral arms cause vertical motions that affect dust distribution and observational signatures in infrared and sub-millimetre wavelengths.

Contribution

It provides a detailed analysis of the vertical motions and dust dynamics caused by spiral arms in planet-induced gaps, highlighting observable effects.

Findings

Spiral arms induce significant vertical gas motions with Mach number of about 0.5.

Dust at the gap edges is stirred vertically, creating a puffed-up appearance.

Infra-red observations are dominated by the thick inner edge of the disc.

Abstract

Giant planets embedded in circumstellar discs are expected to open gaps in these discs. We examine the vertical structure of the gap edges. We find that the planet excites spiral arms with significant (Mach number of a half) vertical motion of the gas, and discuss the implications of these motions. In particular, the spiral arms will induce strong vertical stirring of the dust, making the edge appeared `puffed up' relative to the bulk of the disc. Infra-red observations (sensitive to dust) would be dominated by the light from the thick inner edge of the disc. Sub-millimetre observations (sensitive to gas velocities) would appear to be hot in `turbulent' motions (actually the ordered motion caused by the passage of the spiral arms), but cold in chemistry. Resolved sub-millimetre maps of circumstellar discs might even be able to detect the spiral arms directly.